Uplink power control scheme

ABSTRACT

An uplink power control technique may include a simplified maximum sector throughput (SMST) and a generalized maximum sector throughput (GMST). The SMST and GMST techniques may be used to determine a maximum sector throughput and cell-edge throughput to enhance the overall efficiency of the communication system. The uplink power control technique may determine the optimal uplink power value without collecting interference over thermal noise and without computing the individual channel losses in each neighboring sector.

BACKGROUND

Uplink power control may be used to control the transmit power level tobalance the link performance, terminal battery power, and reduce theinter-sector co-channel interference in uplink. Techniques such as openloop power control (OLPC) and closed loop power control (CLPC) may beused to control uplink power. Open loop power control may be based onchannel loss estimation and the broadcasted information and is generallyused for slow power control. Closed loop power control may be used forfast power control with high signaling overhead induced by unicastcontrol signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention described herein is illustrated by way of example and notby way of limitation in the accompanying figures. For simplicity andclarity of illustration, elements illustrated in the figures are notnecessarily drawn to scale. For example, the dimensions of some elementsmay be exaggerated relative to other elements for clarity. Further,where considered appropriate, reference labels have been repeated amongthe figures to indicate corresponding or analogous elements.

FIG. 1 illustrates an environment 100, which may support maximum sectorthroughput technique to maximize sector throughput and cell edgethroughput in accordance with one embodiment.

FIG. 2 illustrates a block diagram of a mobile node, which may supportsimplified maximum sector throughput (SMST) and generalized maximumsector throughput (GMST) techniques to maximize sector throughput andcell edge throughput in accordance with one embodiment.

FIG. 3 is a flow-chart, which depicts a maximum sector throughputtechnique in accordance with one embodiment.

FIG. 4 is a flow-chart, which depicts a technique to determine spectralefficiency (SE) gain in a home sector supporting a home mobile node inaccordance with one embodiment.

FIG. 5 is a flow-chart, which depicts a technique to determine spectralefficiency (SE) loss in a virtual sector representing neighboring nodesin accordance with one embodiment.

FIG. 6 illustrates a table 600, which includes parameter-valuecombination that reflects the performance of a maximum sector throughputtechnique in accordance with one embodiment.

FIG. 7 is a graph 700, which depicts a relationship between cumulativedensity function (CDF) and throughput in accordance with one embodiment.

FIG. 8 illustrates a table 800 in which spectral efficiency derived forvarious uplink power control techniques are compared in accordance withone embodiment.

FIG. 9 illustrates a radio system 900, which may support the uplinkpower control schemes in accordance with one embodiment.

DETAILED DESCRIPTION

The following description describes embodiments of an uplink powercontrol schemes in broadband wireless networks. In the followingdescription, numerous specific details such as transceiverimplementations, resource partitioning, or sharing, or duplicationimplementations, types and interrelationships of system components areset forth in order to provide a more thorough understanding of thepresent invention. It will be appreciated, however, by one skilled inthe art that the invention may be practiced without such specificdetails. In other instances, control structures, gate level circuits,and full software instruction sequences have not been shown in detail inorder not to obscure the invention. Those of ordinary skill in the art,with the included descriptions, will be able to implement appropriatefunctionality without undue experimentation.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In one embodiment, a uplink power control technique referred to asmaximum sector throughput (MST) technique may be used to maximize thesector throughput and cell edge user throughput. In one embodiment, theMST technique may provide uplink power control without usinginterference over thermal (IoT) noise. In one embodiment, the MSTtechnique may determine spectral efficiency SE_(Gain) for mobile nodesin the home sector after determining a new transmit power (P_(New)) byincrementing a current transmit power value (P₀) by an incrementaltransmit power value (ΔP) using a slow fading technique to determinesignal to interference plus noise ratio (SINR). In one embodiment, theSINR may be determined without using instantaneous channel realization,which may be estimated in advance, which may require substantialcomputational resources and cause processing delay.

In one embodiment, SE_(Loss, E) may be determined in a virtualneighboring sector that may represent an aggregate of interferencessuffered by the neighboring sectors (1 to N) in response to increasingthe transmit power of the home mobile node. In one embodiment, theSE_(Loss, E) may be determined without using downlink preambles sentfrom the neighboring base stations (BS) and noise plus interferencelevel (NI) exchanged and broadcasted among neighboring BS. In oneembodiment, the SE_(Gain) and SE_(Loss, E) may be used to determine anoptimal power P_(Tx) ^(opt) to maximize the overall throughput. In oneembodiment, the SE_(Gain) and SE_(Loss, E) may be further used toenhance cell edge throughput as well.

An embodiment of an environment 100 in which maximum sector throughput(MST) technique may be used to maximize sector throughput and cell-edgethroughput is illustrated in FIG. 1. In one embodiment, the environment100 may comprise home sector 101, neighboring sectors 102-A to 102-D,and a virtual sector 170. In one embodiment, the home sector 101 mayinclude a home mobile node (HMN) 105. In one embodiment, the HMN 105 mayinclude a cell phone, smart phone, personal digital assistant (PDA),mobile internet devices (MIDs), laptops, and such other computingsystems. In one embodiment, the sector 101 is shown comprising a cellphone 105 as an example. In one embodiment, the HMN 105 may representany device, which may support wireless technologies such as thirdgeneration partnership project (3GPP), worldwide interoperability formicrowave access (WiMAX), and long term evolution (LTE).

In one embodiment, the HMN 105 may use a variety of multiple accesstechniques such as frequency division multiplexing (FDM), time divisionmultiplexing (TDM), coded division multiplexing (CDM), orthogonalfrequency division multiplexing (OFDM), and single carrier frequencydivision multiplexing (SC-FDM) and others. In one embodiment, the HMN105 may be coupled to a home base station HBS 110. In one embodiment,the home sector 101 may be surrounded by neighboring sectors 102-A to102-D, which may, respectively, comprise neighboring mobile nodes 120-Ato 120-D. In one embodiment, the neighboring mobile nodes 120-A to 120-Dmay be, respectively, coupled to neighboring base stations NBS 130-A to130-D.

In one embodiment, the HMN 105 may be provided with a current transmitpower value (P₀) to transmit information packets to a destination mobilenode provisioned either within the home sector 101 or the neighboringsectors 102-A to 102-D. In one embodiment, the HMN 105 may send theinformation packets to the HBS 110. In one embodiment, to enhance theuplink performance such as sector throughput and cell edge throughputwithin the home sector 101, the uplink transmit power may be increasedby incrementing the current transmit power value (P₀) by a incrementalpower value (ΔP) to cause a new transmit power value (P_(New)). However,increasing the uplink transmit power value to a new transmit power value(P_(New)) may cause interference to NMN 120-A, 120-B, 120-C and 120-D,which may be operating in a same frequency channel in the neighboringsectors 102-A to 102-D, respectively, and may decrease the linkperformance in the neighboring sectors 102-A to 102-D.

In one embodiment, the MST technique described below may be used tobalance link performances in the home sector 101 and neighboring sectors102 to maximize overall sector throughput and cell edge throughput. Inone embodiment, to predict the effective SE_(Loss, E) in all neighboringsectors 102, a virtual sector such as the virtual sector 170 may beused. In one embodiment, the aggregate of interferences caused by thenew transmit power value (P_(New)) on the base station VBS 160 mayprovide an estimate of effective SE_(Loss, E).

An embodiment of the HMN 105, which may support techniques to maximizesector throughput and cell edge throughput is illustrated in FIG. 2. Inone embodiment, the HMN 105 may comprise an interface 201, a controller205, a power management block 309, one or more transceivers 210-A to210-N, a switch 230, and an antenna 290. In one embodiment, the blockdiagram 200 may be a provisioned as a portion of a network interfacecard in other scenarios such as a computer platform, a laptop computer,a mobile internet device, handhelds, smart phones, televisions and suchother systems.

In one embodiment, the interface 201 may couple the HMN 105 to the homebase station HBS 110. In one embodiment, the interface 201 may providephysical, electrical, and protocol interface between the HMN 105 and theother blocks. In one embodiment, the controller 205 may maintain a trackof the transceivers 210 that may be operational. In one embodiment, thecontroller 205 may control the modulation and demodulation techniquesselected by the transceivers 210. In one embodiment, the controller 205may control communication parameters such as the transmission rate, biterror rate, and other such parameters.

In one embodiment, the transceiver 210-A may comprise a transmitter 250and a receiver 270. In one embodiment, each of the transceiver 210-B to210-N may comprise a transmitter and receiver similar to the transmitter250 and the receiver 270 of the transmitter 210-A. In one embodiment,while receiving the signals from the antenna 290, the receivers such asthe receiver 270 of the transceivers 210-A to 210-N, may receive thesignal from the antenna 290 through a switch 230. In one embodiment,while transmitting the signals, the transmitters such as the transmitter250 of the transceivers 210 may provide the radio signal to the antenna290 through the switch 230.

In one embodiment, the transmitter 250 may receive signals to betransmitted from the controller 205 or directly form the interface 201under the control of the controller 205. In one embodiment, thetransmitter 250 may modulate the signals using techniques such as phase,or amplitude, or frequency modulation techniques. In one embodiment, thetransmitter 250 may then transmit the signals to the antenna 290 throughthe switch 230. In one embodiment, the receiver 270 may receiveelectrical signals from the antenna 290 and demodulate the signalsbefore providing the demodulated signals to the controller 205 ordirectly to the interface 201.

In one embodiment, the switch 230 may couple a transmitter of thetransmitters 210 to the antenna 290 on time sharing basis, for example.In one embodiment, the switch 230 may couple a specific transceiver 210to the antenna 290 in response to an event such as a selection controlsignal of the controller 205. In other embodiment, the switch 230 may beprovided with intelligence to couple an appropriate transmitter 210 tothe antenna 290. In one embodiment, the switch 230 may couple theantenna 290 to the transmitter 250 while the transmitter 250 may beready to transmit signals out to a receiver in other system. In oneembodiment, the switch 230 may couple the antenna 290 to the receiver270, while the antenna 290 has generated signals to be provided to thereceiver 520. In one embodiment, the antenna 590 may be coupled to aswitch 530.

In one embodiment, the power management block 209 may support a MSTtechnique to determine an optimal transmit power to maximize the sectorthroughput and the cell edge throughput. In one embodiment, the powermanagement block 209 may provide a current transmit power value (P₀) tothe transmitter 250 to enable the transmitter 250 to transmitinformation packets. In one embodiment, the value of P₀ may be based ona desired link performance. In one embodiment, the power managementblock 290 may increase the uplink transmit power value by incrementingthe current transmit power value (P₀) by a incremental power value (ΔP)to cause a new transmit power value (P_(New)). However, increasing theuplink transmit power value to a new transmit power value (P_(New)) maydecrease the link performance in the neighboring sectors 102-A to 102-Dby causing interference to NMNs 120-A, 120-B, 120-C and 120-D, which maybe operating in a same frequency channel in the neighboring sectors102-A to 102-D, respectively.

In one embodiment, the power management block 209 may use the MSTtechnique described below to determine an optimal transmit power value,which may balance link performances in the home sector 101 andneighboring sectors 102 to maximize overall sector throughput and celledge throughput. In one embodiment, the power management block 209 maydetermine the SE_(Gain) in the home sector 101 and predict the effectiveSE_(Loss, E) in all neighboring sectors 102 by aggregating the effectiveinterference in a virtual sector 170. In one embodiment, the aggregateof interferences caused by the new transmit power value (P_(New)) on thebase station VBS 160 may provide an estimate of effective SE_(Loss, E).

A flow-chart 300 depicting an operation of the HMN 105 to maximizesector throughput and cell edge throughput is illustrated in FIG. 3. Inblock 310, the power management block 209 may determine the new powervalue (P_(New)) by incrementing the current transmit power value (P_(o))by an incremental power value (ΔP).

In block 350, without using interference over thermal (IoT) noise fromthe neighboring base stations NBS 102-A to 102-D, the power managementblock 209 may determine a spectral efficiency change value SE_(change)value. In one embodiment, the power management block 209 may compute thedifference between the SE_(Gain) in the home sector 101 and effectiveSE_(Loss, E) in the neighboring sectors 102-A to 102-D represented as anaggregate or effective interferences in the virtual sector 170 inresponse to change in transmit power value from P₀ to P_(New) (=P0+ΔP).In one embodiment, determining SE_(Gain) and effective SE_(Loss, E) isdepicted, respectively, in flow-chart 400 of FIG. 4 and flow-chart 500of FIG. 5.

In block 370, the power management block 209 may check if theSE_(change) is equal to zero and control passes to block 380 if theSE_(change) has approached zero and to block 390 if the SE_(change) is apositive value. In block 380, the power management block 209 may use thenew transmit power value P_(New) as the uplink transmit power value. Inblock 390, the power management block 209 may use the increment the newtransmit power value P_(New) by adding an incremental power value, whichmay equal ΔP or any other such small value ΔP₁ and control passes toblock 350.

A flow-chart 400 depicting an operation of the HMN 105 to determineSE_(Gain) is illustrated in FIG. 4. In block 410, the power managementblock 209 may determine an original Signal to Interference plus NoiseRatio (SINR_(Orig)) using a slow fading technique without collecting theinstantaneous channel realization values. In one embodiment, theparameters that may be used to determine the SE_(Gain) may be asfollows:

1) Channel Loss: The mobile node such as HMN 105 may enter a network(for example, by entering the home sector 101) and the channel lossbetween the HMN 105 and the HBS 110 may equal CL₀ represented by 141 andthe channel loss between the HMN 105 and the neighboring NMS may equalCL_(i) (wherein ‘i’ may equal 120-A, 120-B, 120-C, 120-D, . . . 120-N)represented by 151, 152, 153, and 154. In one embodiment, the channelloss 151 may be determined using a downlink preamble received from theNBS 130-A. Likewise, the channel loss 152, 153, and 154 may bedetermined using downlink preambles received from the NBS 130-B, NBS130-C, and NBS 130-D, respectively.

2) Noise plus Interference level (NI): At each neighboring base station,the NI may be estimated as sum power of noises and interferences at thatneighboring base station. For example, the NI_130-A at NBS 130-A may beestimated using the information exchanged among the NBS 130 through anetwork backhaul. In one embodiment, the NI may be expressed in terms ofInterference over Thermal (IoT) noise and noise in that sector as shownbelow in Equation (1):

NI=IoT×P _(Noise) +P _(Noise)  Equation (1)

However, determining Channel Loss and NI may consume substantialcomputational resources and cause delay as well.

In one embodiment, the power management block 209 may determine theSE_(Gain) in response to increasing the uplink transmit power value toP_(New). In one embodiment, the SE_(Gain) in the home sector 101 may begiven by the Equation (2) below:

SE _(Gain)=log(1+SINR _(New))−log(1+SINR _(Orig))=log {(1+SINR_(New))/(1+SINR _(Orig))}  Equation (2)

In one embodiment, the power management block 209 may use a slow fadingtechnique to compute SINR_(New) and SINR_(Orig) and the resultingSE_(Gain) may be substantially accurate based on the stochastic average.In one embodiment, the SINR_(Orig) (the signal plus interference noiseratio in the home sector 101) before increasing the current power valueto a new power value may be given by Equation (3) below:

SINR _(Orig)=(P ₀ /CL ₀)/NI ₀  Equation (3)

In block 440, the power management block 209 may determine SINR_(New)after incrementing P₀ by ΔP to cause the new transmit power valueP_(New) (=P₀+ΔP) using slow fading technique and without usinginstantaneous channel realization values. In one embodiment, theSINR_(New) (the signal plus interference noise ratio in the home sector101) after increasing the current power value to a new power valueP_(New) may be given by Equation (4) below:

SINR _(New) ={P ₀ +ΔP)/CL ₀)/NI ₀}  Equation (4)

In block 480, the power management block 209 may determine SE_(Gain),using SINR_(New), and SINR_(Orig) determined, respectively, in Equations(3) and (4). In one embodiment, the SE_(Gain) may be given by Equation(5) below:

SE _(Gain)=log {(1+SINR _(New))/(1+SINR _(Orig))}

=log {[1+(P _(New) /CL ₀ ×NI ₀)]/[1+(P ₀ /CL ₀ ×NI ₀)]}

=log {1+[(ΔP/CL ₀)]/[NI ₀+(P ₀ /CL ₀]}  Equation (5)

A flow-chart 500 depicting an operation of the HMN 105 to determineeffective SE_(loss, E) is illustrated in FIG. 5. In block 510, the powermanagement block 209 may determine an equivalent channel loss (CL_(E))from the HMN 105 to the virtual sector 170, which may suffer aggregateinterferences in the neighboring sectors 102-A to 102-D caused byproviding P_(New) to HMN 105.

To predict the channel loss in the neighboring sectors 102, the powermanagement block 209 may need 1) Channel Loss from HMN 105 to each ofthe NBS 130-A to 130-D; (2) NI for each of the NBS 130-A to 130-D; and(3) uplink transmit power of each NMN 120-A to 120-D provisioned in theneighboring sectors 102-A to 102D, respectively. However, to obtainchannel loss in each sector, the downlink preamble sent from each NMN120-A to 120-D may be used. Also, NI_(i) may be first exchanged betweenthe NBS 130-A to 130-D and then broadcasted. To obtain channel loss(CL_(i)) and (NI_(i)) for each NBS 130-A to 130-D, a complex hardwaremay be needed in addition to incurring high feedback overhead andcomputationally intensive operations. Also, it may be unrealistic toobtain the uplink transmit power value of the NMN 120-A to 120-D, as theNMN 120-A to 120-D may be attempting to increment the uplink transmitpower values.

In one embodiment, to overcome the above disadvantages, the powermanagement block 290 may determine the equivalent channel loss (CL_(E))from the HMN 105 to the virtual sector 170 (or VBS 160) and CL_(E) maybe given by Equation (6) below:

Interference=P ₀ /CL _(E)=Σ_((i=1 to N)) P ₀ /CL _(i)

→CL _(E)=(Σ_((i=1 to N))1/CL _(i))⁻¹  Equation (6)

In one embodiment, the following approximations may be made beforedetermining SE_(Loss, E):

Approximation (1): The equivalent channel loss (CL_(E)) may bedetermined by estimating the CINR for downlink preamble as compared todetermining the channel loss (CLi) for each NBS 130-A to 130-D.

Approximation (2): Also, effective signal to noise ratio (SNR_(E)) inthe virtual sector 170 may be substantially same as the average signalto noise ratio (SNR_(Avg, home,)) in the home sector 101 as the averageSNR levels in the different sectors 102-A to 102-D may not vary at allor may vary little to be significant. In one embodiment, therelationship between the SNR_(E) and SNR_(Avg home) is as shown inEquation (7) below:

SNR_(E)=SNR_(Avg, home)  Equation (7)

Approximation (3): Also, effective noise plus interference ratio(NI_(E)) in the virtual sector 170 may be approximated to noise plusinterference ratio (NI₀) in the home sector 101. In one embodiment, therelationship between the NI_(E) and NI₀ is as shown in Equation (8)below:

NI_(E)=NI₀  Equation (8)

In block 540, the power management block 209 may determine an equivalentoriginal SINR (SINR_(E, Orig)) without determining the channel loss(CLi) for each neighboring sector 102-A to 102-D individually andwithout using the NI_(i) information from the neighboring sectors 102-Ato 102-D. In one embodiment, the SINR_(E, Orig) (the effective signalplus interference noise ratio in the virtual sector 170) beforeincreasing the current power value to a new power value may be given byEquation (9) below:

SINR _(E, Orig)=(SNR _(E) *P _(Noise))/NI _(E)  Equation (9)

In block 550, the power management block 209 may determine SINR_(E, New)at the virtual sector 170 (or VBS 160) after incrementing P₀ by ΔP tocause the new transmit power value P_(New) (=P₀+ΔP). In one embodiment,the SINR_(E, New) (the signal plus interference noise ratio in thevirtual sector 170) after increasing the current power value to a newpower value P_(New) may be given by Equation (10) below:

SINR _(E, New)={(SNR _(E) *P _(Noise))/(NI _(E) +ΔP/CL _(E))}  Equation(10)

In block 580, the power management block 209 may determine an equivalentSE_(Loss, E) using SINR_(E, New) and SINR_(E, Orig) determined,respectively, in Equations (9) and (10). In one embodiment, theSE_(Loss, E) may be given by Equation (11) below:

SE _(Loss, E)=log {(1+SINR _(E, New))/(1+SINR _(E, Orig))}

=log {[1+(SNR _(E) *P _(Noise))/NI _(E)]/[1+(SNR _(E) *P _(Noise))/(NI_(E) +ΔP/CL _(E))]}

=log {1+[(SNR _(Avg,home) *P _(Noise))/NI ₀]/[(SNR _(Avg,home) *P_(Noise))/(NI ₀ +ΔP/CL _(E))]}  Equation (11)

In one embodiment, the power management block 209 may determine theoptimal transmit power P(Optimal). In one embodiment, if the increase inP_(New) leads to a positive SE_(change), the overall sector throughputmay increase and the current power value may be incremented until anegative SE_(change) may be anticipated. In one embodiment, the optimaltransmit power P(Optimal) may be achieved while SE_(change) equals zeroand ΔP tends to zero. In one embodiment, the SE_(change) may be given byEquation (12) below:

SE _(change) =SE _(Gain) −SE _(Loss)=0 (ΔP→0)

P(Optimal)=log {1+[(ΔP/CL ₀)/(NI ₀ +P ₀ /CL ₀)]}

=log {[1+(SNR _(E) *P _(Noise))/NI _(E)]/[1+(SNR _(E) *P _(Noise))/(NI_(E) +ΔP/CL _(E))]}

P(Optimal)=[CL _(E) ×NI ₀×(NI ₀ +SNR _(Avg,home) ×P _(Noise))/SNR_(Avg,home) ×P _(Noise))]−CL ₀ ×NI ₀  Equation (12)

In one embodiment, the uplink power control technique discussed abovemay be referred to Simplified Maximum Sector Throughput (SMST)technique. In one embodiment, a Generalized Maximum Sector Throughput(GMST) technique may be derived from Equation (12) above.

[P(Optimal)/CL ₀ ×NI ₀]=(CL _(E) /CL ₀)×[1+(1/SNR _(Avg,home) ×P_(Noise) /NI ₀)−1,

=SINR _(Target) ={CINR _(Preamble)×[1+(1/SINR _(Avg,home))]−1}  Equation(13)

wherein CINR_(Preamble)=(CL_(E)/CL₀);SINR_(Target)=[P(Optimal)/CL₀×NI₀]; andSINR_(Avg,home)=(SNR_(Avg,home)×P_(Noise)/NI₀). From Equation (13), itmay be seen that GMST technique may be based on SINR_(Target). In oneembodiment, a carrier to interference plus noise ratio for a downlinkpreamble (CINR_(Preamble)) maybe used to measure the tradeoff betweenchannel loss compensation for home sector 101 and neighboring sectors102-A to 102-D IoT control. In one embodiment, as the SINR_(Target) mayrely on CINR of downlink preamble, the power management block 209 maynot estimate individual CL_(i), which may reduce the complexity of theGMST technique substantially.

Also, in one embodiment, the SINR_(Target) may have a fixed relationshipwith the CINR_(Preamble) and as an extension other tunable parametercoefficients may be used. In one embodiment, the Equation (14) below mayprovide an expression for a Generalized Maximum Sector Throughput (GMST)technique.

SINR _(Target)=β×(CINR _(Preamble))^(γ)+α  Equation (14)

wherein ‘γ’ (gamma) may be used for fractional channel losscompensation. By comparing, Equation (13) and Equation (14), it may beseen that SMST technique may be a particular case of GMST technique withα (alpha)=−1, β (beta)=1+(1/SINR_(Avg,home)), and γ=1. In oneembodiment, the GMST technique may achieve improved cell-edge throughputby tuning the parameter set (α, β, γ).

In one embodiment, a low value of SINR_(Target) may reduce thethroughput of users at the edge of the cell and a high value ofSINR_(Target) may increase the interference in neighboring sectors. Inone embodiment, to improve the cell-edge throughput the SINR_(Target)may be limited as shown in Equation (15) below:

SINR_(Min)<=SINR_(Target)<=SINR_(Max)  Equation (15)

From Equation (13), the SINR_(Target) may be determined as shown inEquations (16) and (17) below:

SINR _(Target)=Max{SINR _(Min) ,CINR_(Preamble)×[1+(1/SINR_(Avg,home))]−1]  Equation (16)

SINR _(Target)=Min{SINR _(Max) ,CINR _(Preamble)×[1+(1/SINR_(Avg,home))]−1]  Equation (17)

wherein SINR_(Min) and SINR_(Max) may represent design parameters, whichmay be used to adjust the tradeoff between sector throughput andcell-edge throughput. In one embodiment, the power management block 209may use SINR limitation and IoT control to improve the cell-edgethroughput further. In one embodiment, the IoT level to the virtualsector 170 may be limited to be within a specific range and the limitingrange is depicted in Equation (18) below:

(P _(New) /CL _(i) ×P _(Noise))<=IoT _(Limit) →PNew<=(CLi×P _(Noise)×IoT _(Limit))  Equation (18)

wherein IoT_(Limit) may be used as another tunable parameter whiledesigning a communication system.

A table 600 includes a list of parameter-value combination that may beused to evaluate the performance of the SMST and GMST techniques inaccordance with one embodiment. In one embodiment, the table 600 maycomprise two columns—parameter list 610 and value 650. In oneembodiment, the parameter list 610 and the corresponding values 650 maycomprise bandwidth (=10 Mhz) for each sector, frequency reuse (=1), celldeployment (=3 sectors and 19 cell wrap-around), number of users(10/sector), number of strong interference (=8), channel model(=E-ITUPed B 3 km/h), permutation mode (=WiMax UL), Uplink symbols(=15), and the site-to-site distance (=500 meters). In one embodiment,using the above listed parameters and the values, the followingtechniques may be evaluated:

-   -   T1: Maximum power technique: All mobile nodes 105 and 120-A to        120-D may use full power without any power control mechanism;    -   T2: SNR-target based technique: Power may be set such that the        received SNR at the base stations may attain a predefined target        i.e., P₀=SNR_(Target)×P_(Noise)×CL₀, wherein SNR_(Target)=7 db;    -   T3: SMST+SINR_(Min)+SINR_(Max) technique: wherein SINR_(Min)=0        db and SINR_(Max)=20 db;    -   T4: SMST+IoT_(Limit) technique: wherein IoT_(Limit)=7 db;    -   T5: SMST+SINR_(Min)+IoT_(Limit) technique: wherein SINR_(Min)=0        db and IoT_(Limit)=7 db;    -   T6: GMST technique: wherein α (alpha)=−0.9, β (beta)=−0.64, and        γ (gamma)=0.9;

A graph 700 depicting a relationship between the cumulative densityfunction (CDF) and throughput for the above listed techniques T1 to T6is illustrated in FIG. 7. In one embodiment, the throughput in kilobytesper second (kbps) may be plotted along the x-axis 705, and the CDF maybe plotted along the Y-axis 795. In one embodiment, the plot 710, 720,730, 740, 750, and 760 illustrate a relationship between CDF andthroughput while using techniques T1 to T6, respectively. As depicted inthe plots, the plot 760 for a GMST technique provides maximum CDF andthroughput and plots SMST based techniques with SINR_(Min) andSINR_(MaX) limitations combined with IoT_(Limit) may providesubstantially similar CDF and throughput values as may be seen fromplots 730, 740, and 750. However, from plot 710, the maximum powertechnique may provide lesser throughput as compared to SMST basedtechnique and GMST technique. The plot 720 based on SNT Target mayprovide high CDF response but very low throughput. In one embodiment,the SMST based techniques (T3, T4, and T5) and GMST technique T6 may beused to achieve maximum sector throughput and cell-edge throughput aswell as compared to maximum power technique and SNR_(Target) techniques.

A table 800 depicting a spectral efficiency (SE) comparison chart forsector and cell-edge conditions achieved using the techniques T1 to T6is illustrated in FIG. 8. In one embodiment, the table 800 may comprisethree columns—uplink power control (ULPC) technique 810, Sector SE 850,and 5% cell-edge SE 880. In one embodiment, the ULPC technique 810 maycomprise techniques T1 to T6 listed above and the corresponding valuesof throughput in bits per second per Hertz for sector SE and cell-edgeSE may be provided, respectively, in columns Sector SE 850 and 5%cell-edge SE 880.

In one embodiment, for SNR_(Target) technique, the cell-edge SE equaling0.0369 (and throughput=141.3 kbps) may be maximum, however, the sectorSE equals 0.4294 (and throughput=1.6444 Mbps), which may be lowestcompared to other techniques. In one embodiment, for maximum powertechnique, the sector SE 850 may comprise a value of 0.5787 (andthroughput=2.2163 Mbps) and cell-edge SE may equal 0.005(throughput=19.3 kbps). In one embodiment, for SMST based techniques T3to T5, the sector SE values may equal 0.7486 (throughput=2.867 Mbps),0.7609 (throughput=2.9142 Mbps), and 0.7247 (throughput=2.7754 Mbps) andcell-edge SE may equal 0.0199 (throughput 76.3 kbps), 0.0082(throughput=31.5 kbps), and 0.0216 (throughput=82.6 kbps). In oneembodiment, for SMST based techniques T3 to T5, both the sector SE (andthe throughput) and the cell-edge SE (and the throughput) may be optimalcompared to it techniques T1 and T2. In one embodiment, for the GMSTtechnique, the sector SE may equal 0.6426 (throughput=2.4612 Mbps) andcell-edge SE may equal 0.0339 (throughput may equal 129.8 kbps).

In one embodiment, the maximum power technique may result in lowestcell-edge throughput (=19.3 kbps) as interference may be out of control.In one embodiment, the SNR_(Target) technique may provide highestcell-edge throughput (=141.3 kbps) but at the cost of sector throughput(=1.6444 Mbps) as mobile nodes 105 and 120-A to 120-D may be forced tolimit the maximum power to reduce interference. In one embodiment, theSMST based techniques T3 to T5 may achieve highest sector throughputs of2.867 Mbps, 2.9142 Mbps, and 2.7754 Mbps, respectively. However, thecell-edge throughputs of 76.3 kbps, 31.5 kbps, and 62.6 kbps may behigher compared to the throughput for maximum power technique. In oneembodiment, the GMST technique may provide an optimal sector throughputand cell-edge throughput.

An embodiment of a cognitive radio system 900, which may support SMSTand GMST techniques to maximize sector and cell-edge throughput isillustrated in FIG. 9. In one embodiment, the cognitive radio system 900may comprise a baseband 910, a signal transmitter 920, a signal receiver930, a channel and power control block 940, a cognitive radio 950, aspectrum sensing receiver 970, a T/R switch 980, and an antenna 990.

In one embodiment, the antenna 990 may provide a wide frequency band.Such an approach may enable the antenna 990 to be used for transmittingand receiving signals processed using technologies such as Wi-Fi,WI-MAX, UMG, UWB, television signals, and such other similar signals. Inone embodiment, while receiving signals, the antenna 990 may be providedthe signals to the T/R switch 980. In one embodiment, while transmittingsignals, the antenna 990 may transmit the signals received from thesignal transmitter 920. In one embodiment, the T/R switch 980 maycomprise intelligence to switch between the signal transmitter 920 andthe signal receiver 930.

In one embodiment, the spectrum sensing receiver 970 may detectunutilized portions (holes) of the spectrum and use the holes to meetthe demand of the spectrum. In one embodiment, the cognitive radio 950may receive sensing signals from the spectrum sensing receiver 970 andmay generate information on the channels that may be used. In oneembodiment, the cognitive radio 950 may provide such information to thechannel and power control 940.

In one embodiment, the channel and power control 940 may control thechannels and the power consumed by the channels by controlling thesignal transmitter 920 and the signal receiver 930. In one embodiment,the power control 940 may support SMST and GMST techniques to provideoptimal uplink transmit power to maximize sector throughput andcell-based throughput as described above. In one embodiment, the powercontrol 940 may perform functions as described with reference to thepower management block 209 above.

In one embodiment, the signal transmitter 920 may receive signals fromthe baseband 910 and may modulate the signals using techniques such asphase, amplitude, frequency, and orthogonal frequency division (OFDM)modulation techniques. In one embodiment, the signal receiver 930 mayreceive signals from the antenna 990 and may demodulate the signalsbefore providing the demodulated signals to the baseband 910. In oneembodiment, the baseband 910 may receive signals from the processingblocks of the system and may perform baseband processing before sendingthe signals to the signal transmitter 920. In one embodiment, thebaseband 910 may receive demodulated signals from the signal receiver930 and may perform baseband processing before providing the signals tothe processing blocks of the system 900.

Certain features of the invention have been described with reference toexample embodiments. However, the description is not intended to beconstrued in a limiting sense. Various modifications of the exampleembodiments, as well as other embodiments of the invention, which areapparent to persons skilled in the art to which the invention pertainsare deemed to lie within the spirit and scope of the invention.

1. An apparatus to support uplink power control technique, comprising: atransmitter coupled to a channel by an uplink, and a power managementblock coupled to the transmitter, wherein the power management block isto determine an optimal uplink power value without collectinginterference over thermal (IoT) noise from a plurality of neighboringsectors, wherein the optimal uplink power value is to cause an optimalsector throughput and cell-edge throughput.
 2. The apparatus of claim 1,wherein the power management block is to generate a new power value byincrementing a current power value by an incremental power value untilthe new power value reaches the optimal uplink power value.
 3. Theapparatus of claim 1, wherein the power management block is to use asimplified maximum sector throughput (SMST) technique to determine theoptimal uplink power value, wherein the SMST technique includesdetermining a spectral efficiency gain (SE_(Gain)) in a home sector inwhich the mobile node is located and an equivalent spectral efficiencyloss (SE_(Loss, E)) in a virtual sector in response to the new powervalue, wherein a spectral efficiency change is equal to a difference inthe SE_(Gain) and the SE_(Loss, E).
 4. The apparatus of claim 3, whereinthe power management block is to increment the current power value bythe incremental power value until the spectral efficiency change isequal to zero and the incremental power value tends to zero.
 5. Theapparatus of claim 3, wherein the power management block is to determinethe SE_(Gain) using an original signal to interference plus noise ratio(SINR_(Orig)) and a new signal to interference plus noise ratio(SINR_(New)), wherein SINR_(Orig) is determined before incrementing thecurrent power value and the SINR_(New) is determined after incrementingthe current power value.
 6. The apparatus of claim 5, wherein theSINR_(Orig) and the SINR_(New) is determined using a slow fadingtechnique and without using instantaneous channel realization values. 7.The apparatus of claim 3, wherein the power management block is todetermine the SE_(Loss, E) using an equivalent channel loss (CL_(E)) inthe virtual sector, wherein the CL_(E) is representative of aggregatechannel losses in the plurality of neighboring sectors.
 8. The apparatusof claim 7, wherein the CL_(E) is an estimate of a carrier tointerference plus noise ratio (CINR_(Preamble)) of downlink preamble. 9.The apparatus of claim 2, wherein the power management block is to use ageneralized maximum sector throughput (GMST) technique to determine theoptimal uplink power value, wherein the GMST technique is based on asignal to interference plus noise ratio (SINR_(Target)) target.
 10. Theapparatus of claim 9, wherein the SINR_(Target) has a linearrelationship with a carrier to interference plus noise ratio(CINR_(Preamble)) of downlink preamble, wherein the GMST techniqueincludes tunable parameter coefficients to enhance the sector throughputand cell-edge throughput.
 11. A method to support uplink power controltechnique in a mobile node, comprising: generating a new power value byincrementing a current power value by a first incremental value,determining a spectral efficiency gain (SE_(Gain)) in a home sector inwhich the mobile node is located, determining an effective spectralefficiency loss (SE_(Loss, E)) in neighboring sectors surrounding thehome sector without computing individual channel loss in the neighboringsectors and without collecting noise plus interference (NI) level fromthe neighboring sectors, checking if the new power value generates animprovement in overall link performance, and accepting the new powerlevel as an optimal transmit power level if further incrementing of thenew power level causes deterioration of the overall link performance.12. The method claim 11, wherein the uplink power control techniqueincludes a simplified maximum sector throughput (SMST) technique,wherein determining the SE_(Loss, E) includes determining an equivalentchannel loss (CL_(E)) in a virtual sector that is representative ofinterferences suffered by the neighboring sectors in response to the newpower value.
 13. The method of claim 12 comprises determining a spectralefficiency change as a difference in the SE_(Gain) and the SE_(Loss, E).14. The method of claim 13 comprises determining the SE_(Gain) by usingan original signal to interference plus noise ratio (SINR_(Orig)) and anew signal to interference plus noise ratio (SINR_(New)), whereinSINR_(Orig) and the SINR_(New) is determined independent of estimationof instantaneous channel realization.
 15. The method of claim 11,wherein improving the link performance includes increasing sectorthroughput and cell-edge throughput.
 16. The method of claim 14, whereinthe SINR_(Orig) and the SINR_(New) is determined using a stochasticaverage based slow fading technique.
 17. The method of claim 12, whereinthe CL_(E) is an estimate of a carrier to interference plus noise ratio(CINR_(Preamble)) of downlink preamble.
 18. The method of claim 11,wherein the uplink power control technique includes a generalizedmaximum sector throughput (GMST) technique to determine the new powervalue to improve sector throughput and cell-edge throughput, wherein theGMST technique is based on a signal to interference plus noise ratio(SINR_(Target)) target.
 19. The method of claim 19, wherein theSINR_(Target) has a linear relationship with a carrier to interferenceplus noise ratio (CINR_(Preamble)) of downlink preamble.
 20. The methodof claim 19, wherein the GMST technique includes tunable parametercoefficients, wherein the tunable parameter coefficients include a firstparameter to compensate fractional channel loss.